Sustainable Architecture environment - Iran University of...
-
Upload
nguyenkhanh -
Category
Documents
-
view
216 -
download
3
Transcript of Sustainable Architecture environment - Iran University of...
International Journal of Architectural Engineering & Urban Planning, Vol. 25, No. 2, December 2015
Green envelopes classification: the comparative analysis of efficient factors on the thermal and energy performance of green envelopes
E. Najafi1, M. Faizi
2,*, M.A. Khanmohammadi
3, F. Mehdizadeh Saradj
4
Received: April 2015, Accepted: May 2015
Abstract
This paper classifies green envelopes as green roofs and green walls according to effective factors, which were derived
from literature to compare the green envelopes’ thermal and energy performance in a more effective way. For this purpose, an
extensive literature review was carried out by searching keywords in databases and studying related journal papers and
articles. The research method for this study was bibliographic and logical reasoning. The paper proposes five classification
factors: contextual factors, greenery factors, scale factors and surface and integration factors. It also demonstrates the
influence of physical and geometrical properties of plants and their supporting structures on the thermal performance of green
envelopes. The paper argues that climatic conditions also have an important role on the thermal behavior of green envelopes
and it determines the types of greenery integration into building envelopes.
Keywords: Green roof, Green wall, Thermal function, Energy performance, Living envelope.
1. Introduction
Green envelopes in this paper are defined as any surface
of the building envelope with greenery. Usually these green
surfaces are known as green roofs and green walls. Using
greenery on building exterior surfaces dates back to a long
time ago. From a certain point of view, it was foliage and
tree branches that made the first houses for human beings
[1]. The hanging gardens of Babylon, which date back to
2000 to 3000 years ago, were one of the most famous
examples of using greenery on building surfaces [2].
Another example is traditional Scandinavian sod roofs with
their low slope and good thermal insulation, which were
common in many rural areas of Scandinavia [3]. Also, from
3rd century BC until 17th century AD, the Romans used
trellises for growing grape on villa walls [4].
Modern greenery systems on roofs can be divided into
the two main types of extensive and intensive systems
[5-7]. Intensive and extensive green roofs have the same
* Corresponding author: [email protected]
1 PhD Student, School of Architecture and Environmental
Design, Iran University of Science and Technology, Tehran, Iran
2 Full Professor, Department of Landscape Architecture School
of Architecture and Environmental Design, Iran University of
Science and Technology, Tehran, Iran
3 Assistant Professor, School of Architecture and Environmental
Design, Iran University of Science and Technology, Tehran, Iran
4 Associate Professor, Department of Conservation of historic
buildings and sites school of Architecture and Environmental
Design, Iran University of Science and Technology, Tehran, Iran
constituting layers: from top to bottom: (1) vegetation, (2)
substrate, (3) filter membrane, (4) drainage layer, and (5)
root resistance layer. Plants cultivated on green roofs range
from native plants and grasses to drought tolerant types
such as Sedum and Delosperma species, which belong to
the cactus family of plants [8-13] [Fig. 1].
Intensive green roofs are frequently designed as public
places and include mostly herbal perennial plants, trees,
shrubs, and hardscapes similar to landscaping found at the
ground level. They generally require substrate depths
greater than 20 cm to 120 cm and ‘intense’ maintenance.
In comparison, extensive green roofs are lighter and
cheaper with lower capital cost and need less maintenance.
The substrate depth for extensive roofs is between 5 cm
and 15 cm, which can grow slow growing plants with low
height and weight such as grass, herbs or drought-tolerant
sedum [5, 14-20].
Green walls or green vertical systems can also be
divided into two different categories according to the level
of maintenance and variety of plant types that can be used
in them. Intensive green walls need more care and use
more types of plants [21] [22]. However, green walls are
usually classified into green façades and living walls
according to the type of plants (climbing or non-climbing)
and the place of plantation [21, 22]. Green façades use
climbing plants to climb on the façade surface or a
structure connected to the façade and their growing
medium is almost at the foot of the façade on ground or in
the pots at different heights of the building [21, 22]. Green
façades have three types: traditional green facades, double-
skin green façades and green curtain and perimeter flower
pots [21]. In traditional green façades the plants stick to
the façade while in double-skin ones a supporting structure
Sustainable Architecture environment
Dow
nloa
ded
from
ijau
p.iu
st.a
c.ir
at 2
:40
IRD
T o
n F
riday
Jun
e 1s
t 201
8
[ DO
I: 10
.220
68/ij
aup.
25.2
.100
]
E. Najafi, M. Faizi, M.A. Khanmohammadi, F. Mehdizadeh Saradj 101
will support them [Fig. 2.a]. Double-skin façades have
different systems like modular trellises, wired, and mesh
structures [21-23] [Fig. 2.b]. Living walls are made of
panels and/or geo-textile felts, which are fixed to a vertical
support or on the wall structure [Fig. 2.c, 2.d]. Living
walls support growth medium in felts or panel modules
and boxes as a parts of the wall structure and the building
[21]. Living walls sometimes contain pre-cultivated panels
or felts to be developed [22].
Green envelopes include green walls and green roofs and
other exterior surfaces of the building which can be covered
by vegetation [24]. Greening these surfaces by vegetation
have different thermal and energy performances. These
various functions can be categorized and compared according
to a given criteria. The thermal properties and energy
efficiency of green surfaces in buildings depend on many
factors, which can be categorized as: contextual factors,
greenery factors, scale factors, surface factors, and integration
factors. Contextual factors refer to climatic conditions,
economic factors, technical aspects, structural factors.
Greenery factors include the vegetation’s physical and
biophysical properties. Scale factor refers to the scale of the
built environment, which can be influenced by the greenery
itself and the scale of the time used for assessing the thermal
and energy performance of green envelopes. Surface factor
are the characteristics of a building envelope’s surface such as
its orientation and position. Finally, integration factor is
related to the way that vegetation is integrated into the
building envelope’s surface.
Fig. 1 The common layers of a green roof.
Fig. 2 (a) Green façade, the growth medium for plant is on the ground. (b) Double skin green façade, an additional structure standing beside
the wall supports the greenery. (c) Modular panel living wall, the growth medium is in every box panel. (d) Geotextile living wall, the growth
medium is in the felt layers or packets sticking or hanging from the wall
(a) (b)
(c) (c) (d)
Dow
nloa
ded
from
ijau
p.iu
st.a
c.ir
at 2
:40
IRD
T o
n F
riday
Jun
e 1s
t 201
8
[ DO
I: 10
.220
68/ij
aup.
25.2
.100
]
102 International Journal of Architectural Engineering & Urban Planning, Vol. 25, No. 1, June 2015
2. Contextual Factors
There is much research about the energy saving
benefits of green envelopes and their role for passive
cooling. Although these researches studying the thermal
and energy performance of green envelopes belong to
different geographical locations, only a few refer to the
climatic conditions and their role in the parameters of the
study. Here the context of different studies that considered
the climatic factors is categorized according to Köppen
climate classification [5, 6, 8, 17, 18, 25-42].
2.1. Green roof contextual factors
There were several studies considering the thermal
properties and energy efficiency of green roofs in different
climatic conditions [Fig. 3]. S.W. Tsang et al studied a
green roof in the tropical climate of Hong Kong and
evaluated its thermal and energy performance in a
theoretical model and found some dependencies between
the green roof’s thermal properties and environmental
factors. The research demonstrates that latent heat
dissipation is more efficient in tropical climate than in
temperate climates, especially in sunny summer days,
where it is twice other days. Comparing a green roof with
a bare roof demonstrates the absorption of solar radiation
depends more on shortwave radiation than long wave
radition, and the heat storage and sensible heat of a bare
roof is more than that of a green roof. But increasing soil
water would increase its heat storage. A green roof’s
albedo is twice that of a bare roof. Increasing in
convection coefficient causes greater latent heat
dissipation for both roof types [43].
Another investigations about extensive green roof was
conducted in Athens, Greece, in the Mediterranean
climate. This study shows that a green roof can reduce
cooling energy in the summer by about 40%, but the
reduction of heating energy in the winter is small [10, 44].
In Midwestern U.S. climate with hot-humid summers and
cold-snowy winters, an extensive green roof has lower
heat flux than a bare roof in all seasons, especially in
summers. This indicates the energy saving properties of
green roofs with more effectiveness in summer. Also a
bare roof has more temperature fluctuations than a green
roof during the year [45]. In the cold weather of Ottawa,
Canada, extensive green roof empirical experiments
demonstrate the reduction and modification of roof
temperature fluctuations with moderating heat fluxes
mostly in warmer months. Daily Energy consumption
reduces about 75% in summer days [46].
Comparing the impact of latitude on the efficiency and
energy performance of extensive green roof was explored
in Mediterranean area with three different latitudes.
Barcelona was selected in the north with Cairo in the south
and Palermo in the middle, all in mild climates but with
differences in rainfall, air temperature and humidity, which
depend on solar radiation and geographical latitude. These
are important factors to determine the energy needs of
buildings, considering the climatic conditions. The
northern region depends more on heating, while the middle
region needs both heating and cooling, and the southern
region has more cooling needs. The results show the
importance of soil water content for more effective
cooling. But good heating performance was achieved with
dry soil, which means lower energy to heat. So soil
moisture acts differently depending on thermal needs [47].
The cooling effect of extensive green roof proved to be
adequate for the warm summers of Yamuna Nagar in India
with a humid-subtropical climate [48]. Extensive green
roofs can contribute to energy efficiency in buildings
within the temperate climate of Florianopolis, Brazil
through reducing heat gain in warm seasons about 92%
and increasing heat loss about 49% in comparison with
ceramic roofs. In the cold season, green roofs reduce heat
gain by 70% and reduce heat loss by about 44% in
comparison with ceramic roofs [49]. Another study shows
improvement in thermal comfort and energy performance
using extensive green roofs in La Rochelle, France [50].
The climate has a significant effect on transpiration rate
and so the latent heat loss and energy transmission of the
roof.
The highest rate of performance is in autumn for the
tropical climate of Hong Kong. Wind has no significant
effect on heat loss in different seasons. Heat dissipation is
not enough as the result of high humidity and dense plant
leaves in the summer. Climatic factors have an important
role to determine the temperature at different heights of the
canopy and the soil surface. These factors are not
significant in determining the temperature and humidity in
different depths of the soil. In winter, intensive green roof
dissipates great heat flux to the ambient air, which
necessitates more energy to warm the indoor spaces. The
intensive green roof has an opposite performance in the
cold seasons of temperate climates, because it functions as
thermal insulation and reduces the heat flux to ambient air.
In this case, lower amounts of energy are needed for
heating in cold seasons of such climates. When raining,
because of soil water absorption, the heat capacity of the
soil increases and it saves more energy relating to heat
storage and soil insulation performance [16]. Intensive
green roofs in the humid subtropical climate of Hong
Kong show very good thermal performance. Even 10 cm
soil thickness is enough to prevent heat penetration into
the interior spaces. Seasonal weather conditions have
important impact on cooling performance of the roof [51].
An intensive green roof with 100 cm soil thickness in
Hong Kong was explored for its components thermal
function. The tree canopy would decrease the direct
radiation on the roof by creating shading, while at the
same time, it prevents air movement on the roof surface
and increases air temperature. The substrate reduces the
thermal fluctuations of the roof. Also the roof has good
thermal insulation properties in the warm season and
seasonal weather conditions affect transpiration of the
plants on the roof and control the cooling impact of the
roof [51].
Dow
nloa
ded
from
ijau
p.iu
st.a
c.ir
at 2
:40
IRD
T o
n F
riday
Jun
e 1s
t 201
8
[ DO
I: 10
.220
68/ij
aup.
25.2
.100
]
E. Najafi, M. Faizi, M.A. Khanmohammadi, F. Mehdizadeh Saradj 103
Fig. 3 Green roof studies that consider climatic factors in different climates such as arid, tropical wet, mediterranean, humid subtropical,
marine west coast, humid continental
From the economical and structural point of view,
extensive green roofs have the advantage of having lower
weights and costs for construction and maintenance in
comparison to intensive green roofs. So the extensive
green roof has the potential to be installed on existing
building roofs and roof retrofittings, and it can help
creating thermal insulation and better energy performance
in older buildings in the UK climatic conditions [7].
Vegetation development over time (three year) on
extensive green roofs in Sweden demonstrates an increase
in moss growing in the substrate. Sedum album and sedum
acre were the most surviving species. There is a need for
the development of other green roof techniques, because
existing techniques have a low potential for creating
biodiversity in plant types [26].
Fig. 4 Green wall studies done so far considering climatic factors in different climates such as Tropical wet, Mediterranean, Humid
continental
2.2. Green walls’ contextual factors
Plants on the façade have different advantages
considering the climatic conditions and seasons [Fig. 4]. In
warm climates and seasons, they produce a cooling effect
as a result of shading and cutting solar radiation, while in
cold climates and seasons, evergreen plants function as
thermal insulation. So generally, greenery on the facade
can help create a more efficient thermal performance and
so more energy saving [45]. Investigating energy saving
properties of green façades in the dry Mediterranean
Continental climate of Spain came to the conclusion that
because of greenery shading, a microclimate in the cavity
between greenery and the wall is created, which has a
lower temperature and higher relative humidity in
comparison to ambient air. Moreover, the greenery also
works as a wind barrier. But, there was no conclusion
about the green wall insulation properties [39]. Another
research in Spain addresses the energy saving and storage
of green roof and double skin green façades in autumn and
Dow
nloa
ded
from
ijau
p.iu
st.a
c.ir
at 2
:40
IRD
T o
n F
riday
Jun
e 1s
t 201
8
[ DO
I: 10
.220
68/ij
aup.
25.2
.100
]
104 International Journal of Architectural Engineering & Urban Planning, Vol. 25, No. 1, June 2015
winter. This research came to the conclusion that in such a
climate, a slight increment in the temperature was
observed in the distance between the greenery and the wall
(in comparison with ambient air) and there was a low
reduction of wall surface temperature [23]. In the tropical
climate of Singapore, the effect of different green walls on
thermal comfort and energy consumption was studied and
their thermal insulation performance was proved [52].
From an economic point of view, a direct green façade
is the cheapest green wall system, because of its low
maintenance and the materials needed to support it. On the
other hand, living walls and indirect green facades are
expensive types because of the design complexity,
supporting structure and more maintenance and materials
needed to maintain the greenery [53]. All the studies
demonstrate the green wall thermal effectiveness in cold
and warm seasons, which lead to more energy efficiency.
3. Greenery Factors
Greenery factors include the vegetation’s physical and
biophysical properties. Physical properties of plants refer
to their height, foliage density and geometry with
dimension characteristics [Table 1], while biophysical
properties are related to transpiration, photosynthesis and
evapotranspiration characteristics of the plants [Table 2]
[16].
Table 1 Greenery physical properties for green roofs and green walls which are mainly mentioned in the literature
Green roofs Plant height color 𝐿𝐴𝐼 =Leaves Area
Substrate Area Foliage density Plant species
Green walls Leaf shape Foliage density Shading coefficient Greenery coverage ratio
Table 2 Greenery biophysical properties for green roofs and walls (envelopes)
Green envelopes Photosynthesis Absorption Evapotranspiration Convection Reflection
Plants create shading and so they cut direct solar
radiation on surfaces and therefore prevent heating from
radiation. Also, their leaves have transpiration and
photosynthesis which absorbs solar radiation and convert
sensible heat to latent heat. So they can reduce ambient air
temperature.
3.1. Green roof greenery factors
Plants suitable for extensive green roofs in the Humid
Subtropical Climates of Taiwan have better cooling effects
considering their height, color and type. This resulted in an
optimum height of 35 cm followed by heights of 15 cm
and 10 cm respectively. Also plants with green leaves
other than red and purple have better cooling effects. It is
better if plants are chosen for their drought resistance [31].
Heat flux of extensive roof is sufficient to keep indoor
temperature at 25º C in average in New Delhi, India. The
cooling function of the roof is related to the Leaf Area
Index of greenery to be 4.5. LAI is an important factor for
creating a microclimate distinguished from ambient under
vegetation canopy. The increasing LAI leads to a reduction
of air temperature and its fluctuations under canopy and
decreasing of heat flux penetration to indoor spaces, while
it also increases the thermal insulation of the roof [48].
Foliage density is proved to be an effective physical
parameter for extensive green roof thermal performance
and energy balance. In a summer day there was a 30°C
difference between the green roof and the concrete slab
outer surface temperature and generally the temperature
changes was correlated with foliage density directly [50].
Biophysical properties of extensive green roof affect its
thermal energy balance with water saturated soil.
Evapotranspiration have the most impact on heat dissipation
and then it is long wave radiation emissions to cool the roof.
Photosynthesis absorbs heat and prevents it from penetrating
into indoor spaces. Soil and plants heat storage is less than
1% of the whole thermal energy gain. Almost all of the roof
heat gain is related to solar radiation and convection is
negligible. Considering green roof different layers and the
role of each one in thermal function of the roof, sedum heat
gain is 99.1% from solar radiation with only 0.9% from
convection. Biophysical functions of the greenery contribute
to roof heat dissipation, which accounts for
evapotranspiration, long wave reflection and photosynthesis
being 58%, 30.9% and 9.5% respectively. Only 1.2% of
total heat gained would be stored in green roof and
transmitted to indoor spaces [54]. Planting drought enduring
plants with large coverage ratio and burned sludge substrate
lead to better thermal function of green roof in the south
Taiwan climate [55, 56].
3.2. Green wall greenery factors
Simulation of green wall thermal function on different
façades shows that greenery coverage is completely
effective in decreasing the mean radiant temperature of
glass facades. Also for having more cooling effects and
more thermal insulation, the shading coefficient of plants1
needs to be low and this has linear correlation with leaf
area index in a negative way. Greenery coverage is a more
influential factor than shading coefficient. Optimum
results are obtained with high leaf area index and low
shading coefficient, which are the result of more density
and covering ratio of foliage [52].
Ivy covered green walls with a supporting grid was
mathematically modeled to investigate its thermal function
affected by physical and geometrical properties of the
green wall. The main greenery physical variations were
considered as: covering ratio¹, green density² and leaf
shapes³. The main factors controlling green wall thermal
Dow
nloa
ded
from
ijau
p.iu
st.a
c.ir
at 2
:40
IRD
T o
n F
riday
Jun
e 1s
t 201
8
[ DO
I: 10
.220
68/ij
aup.
25.2
.100
]
E. Najafi, M. Faizi, M.A. Khanmohammadi, F. Mehdizadeh Saradj 105
function are greenery density, covering ratio and
geometrical properties of supporting grid. Heat flux
transition to building increases as a result of larger
distance of grid cables to a critical point and decreasing in
foliage covering ratio. Covering ratio is the most important
factor influencing heat flux. If its value is less than 30%,
its thermal function is much like a bare wall. But if
coverage ratio is 100%, it can cut solar gain up to 40%.
Shaded area of the wall is not only determined by
coverage ratio but also by foliage density. Foliage density
equals coverage ratio when it is 1 and it can affect
reducing heat flux to indoor up to this rate. Larger amounts
of foliage density slightly decreases the heat flux to indoor
spaces [57-63] .
There was no study considering the biophysical
properties of plants influencing the thermal function of
green vertical systems.
4. Scale Factors Impact
Greenery has many advantages as it conditions the
climatic factors in different scales. Scale factor takes into
consideration the scale of the greenery impacts from energy
and thermal point of view which can be categorized into
three scales: macro-scale for urban areas, meso-scale for
buildings and micro-scale for building parts or elements.
4.1. Green roof impact scale factors
Green roofs’ benefits have been explored in the two
scale of building and urban area in New York City.
Vegetation density decreases the air temperature of an
urban area, while in the building scale, it increases the roof
albedo and thermal resistance of roofs because of the
plants’ biophysical processes. Monitoring four locations in
New York City to investigate the influence of the green
area on air temperature shows a 2degrees C difference
between the largest and smallest green areas’ temperature.
The surface albedo is an important factor to determine
roofs’ thermal behavior. White and green roofs have
greater albedos than a black roof. Extensive green roof
thermal insulation is mainly affected by its albedo and its
vegetation biological activities. Also green roofs can
decrease the maximum energy consumption of buildings.
Changing black roofs to green roofs would affect the
thermal function of roofs in a positive way and so reduce
energy consumption in different scales of building and
urban areas [30]. Green roofs can increase green areas in
cities. Green sites would decrease air temperature, which
can be on average about 0.9°C cooler than bare sites in UK
parks. The greater green area and more tree numbers
would result in more cooling effects in days. This is
despite the fact that there is a need for future studies on
greenery types and its distribution on cooling effect [64].
30
31
32
33
Late
Aft
ern
oon T
em
pra
ture
Rural Commercial City Urban
Residential
Rural
FarmlandSuburban
Residential
Park
Urban Heat Island Effect
Suburban
Residential
Fig. 5 Urban Heat Island effect, shows increase in temperature over cities. Green roofs can help decrease in temperature in large scale for
urban areas
15
25
35
45
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Tem
pera
ture
(c)
Time (hour)
Green Roof Temperature
Conventional Roof Temprature
Fig. 6 Comparing green roof temperatures with conventional roof temperatures during a 24 hours period shows much less fluctuations in
temperature with less need for cooling. It is the small-scale impact of green roof on energy consumption
Dow
nloa
ded
from
ijau
p.iu
st.a
c.ir
at 2
:40
IRD
T o
n F
riday
Jun
e 1s
t 201
8
[ DO
I: 10
.220
68/ij
aup.
25.2
.100
]
106 International Journal of Architectural Engineering & Urban Planning, Vol. 25, No. 1, June 2015
Considering that plants’ CO₂ consumption during the
day is more than night, they can reduce CO₂ concentrations in ambient air. An extensive green roof
with low height plants and an area of 16 m² in a sunny day
in the tropical climate of Hong Kong shows a 2%
reduction in CO₂ levels. Reducing CO₂ concentration in
the environment depends on plants conditions, air flow,
and the position of the green roof [17].
3.4. Green walls impact scale factor
Mechanism of passive cooling in green walls is related
to the shadow creation by leaves, solar heat absorption and
dissipation by greenery which act as thermal insulation
and cooling through evaporation and vegetation
transpiration. Green walls reduce wind velocity by acting
as wind barriers. Exploring a double skin green wall
demonstrates the creation of a microclimate between
greenery and wall with lower temperature and higher
relative humidity than the ambient air in dry continental
climatic condition of Mediterranean region [21].
Sensible reduction of minimum air temperature
through large regions occurs while increasing greenery
covering ratio of facades. Green walls can reduce urban
heat island effect with greenery coverage ratio as the most
influencing factor [52].
5. Building Envelope Surface Factors
The materials and layers of building envelope surfaces
can make a big difference in the thermal behavior and
energy efficiency of the surface, which accomodates the
greenery. Building envelope includes different surfaces
with different positions and directions which cause
differentiation in their thermal properties and therefore
energy performance. Roofs as horizontal surfaces, receives
more radiation in summers, while walls are vertical
surfaces which receive direct radiation according to their
geographic direction [65].
5.1. Green roof surface factors
For the most part, green roof thermal properties were
explored considering greenery thermal function. Studying
thermal properties of abiotic parts of green roof in Hong
Kong shows different results with regards to decreasing
thermal insulation of densely vegetated green roofs in
comparison with bare roofs in temperate climates. A water
storage layer, with its water content has the evaporative
cooling role that increases the specific heat capacity of the
roof. The drainage layer with its porous structure contains
stagnant air, which increases the roof’s thermal resistance
and insulation [9] [Table 3]. Comparing different roof types
in Kobe Japan, demonstrates that extensive green roofs have
low heat flux like high-reflecting white roofs because of the
greenery evapotranspiration, which cause large latent heat
flux. But the gray high reflective roof and concrete roofs
have large sensitive heat flux [20, 45, 66-68].
The influence of mass transfer of green roofs, aside
from its heat transfer, was ignored in most studies, though
latent heat in condensation and evaporation processes
conveys energy. Findings show that heat and mass transfer
have different processes in green roofs in comparison with
bare classical roofs. Green roofs improve the thermal
behavior and energy saving of the building. As using
hygroscopic materials in the building reduces the energy
consumption, the importance of moisture factor in green
roofs becomes obvious [50].
Table 3 Thermal function of green roof layers [9].
Roof layer Water storage Drainage
Thermal function Increasing evaporative cooling Increasing thermal resistance
Increasing specific heat capacity Decreasing heat transfer
5.2. Green wall surface factor
The influence of wall direction on green wall energy
efficiency was investigated and the results show a small
difference in air temperature between wall and greenery in
south directions which has the least value for south east
and the most for south west direction. The east direction
facades as (N.E, E, and S.E) have the lowest temperature.
The south west façade had the highest relative humidity
among others [23].
6. Integration Factors
Integration factors refer to the way greenery is
integrated into the building envelope. This is mainly
related to the green roof or green wall type or the
arrangement of different parts and layers in the building
envelope [61, 69].
6.1. Green roof Integration factors
Inverted roofs would decrease the merits of a green
roof. Inverted extensive green roofs have smaller thermal
fluctuations and lower peak temperatures in comparison
with inverted gravel ballasted roof in Michigan, USA.
Extensive green roofs reduce heat transition through roofs
by about 167% in summer as the highest rate and 13% in
winter as lowest rate in comparison with gravel roofs. The
most important factors, which affect the different
performance of the roofs, are air temperature, solar
radiation and the amount of moisture in the growing
medium. Snow is a controlling factor in winter. Extensive
green roof reduces energy consumption during a year. The
decrement of energy consumption is determined by
climatic condition, roof type, plant types, growing media
depth and composition, and the amount of irrigation.
Increasing the growing medium’s depth increases the
leaves area and biomass with more biophysical effects and
Dow
nloa
ded
from
ijau
p.iu
st.a
c.ir
at 2
:40
IRD
T o
n F
riday
Jun
e 1s
t 201
8
[ DO
I: 10
.220
68/ij
aup.
25.2
.100
]
E. Najafi, M. Faizi, M.A. Khanmohammadi, F. Mehdizadeh Saradj 107
impact. In tropical climatic conditions, the results may be
not the same and plant type selection would be different
[45]. The roof garden in Hong Kong has different
ecological and energy performance in comparison with an
extensive type. It has lower transpiration rate and thus
lower latent heat loss. Intensive green roofs create a
distinguished microclimate under their canopy. The
canopy slows down the wind and stores heat released by
the roof so its heat loss is decreased and its thermal
resistance is reduced relatively. But its heat loss is
buffered in rainy weather. The canopy cut 80% of solar
radiation reaching the soil and roof and its albedo differs
according to wavelength from 40% for near infrared
radiation to 6% for photosynthetic active radiation.
Tropical intensive green roofs have less thermal insulation
and cooling efficiencies in comparison with temperate
climate regions [14].
6.2. Green wall integration factors
The thermal performance of different green wall types
was examined in Singapore. Living wall types as
Modular panel, Grid and modular ones have the best
cooling effects for maximum wall surface temperature.
Reducing the diurnal temperature fluctuations of wall
surfaces and ambient air is achieved more effectively by
living wall with modular panel. This is while Green
façade type as Modular trellis had no considerable impact
on reducing ambient air temperature [70]. The impact of
different types of green wall systems on ambient air
velocity and temperature as well as wall surface
temperature was explored and compared with bare wall
in three different cities of Netherland. All green walls
have lower surface temperatures in comparison with bare
wall thanks to their leaves shading. Also wind velocity
reduction was observed inside foliage and the cavity
behind, which increases the thermal insulation of the wall
in direct green façades. Living wall with planter boxes is
the most effective wind barrier than other types because
of its air cavity. Also it shows more thermal insulation
efficiency in cold weather. But the cavity thickness has
an optimum size between 4 to 6 cm to decrease wind
velocity. All these studies demonstrate the green walls’
thermal effectiveness in cold and warm seasons which
lead to more energy efficiency [53].
7. Discussion
Exploring energy performance of building envelope
surfaces depends on their thermal function. As the sun
path changes during a day and a year, the sun position and
geographical latitude determine the amount of solar
radiation reaching the earth. On the other hand, the
greenery and surface properties affect the green envelope’s
thermal behavior and so it’s energy performance.
Reviewing existing literature shows that there is a gap
in comparing energetic performance of green roofs with
green walls. This is may be due to their different structural
system and position. But, considering the fact that
horizontal surfaces receive more solar radiation with
greater intensity in summers than vertical surfaces, it is
safe to assume that their heat gains are more. It can be
concluded that green roofs can have more cooling effects
than green walls because reducing their heat gain by
greenery will help create more cooling. But there are other
factors to be considered, such as the ratio of roof area to
the building volume, or the size of roof area in comparison
with the area of the walls. Another gap in data is the lack
of adequate studies about certain types of green envelopes
over the others. For instance studies about intensive green
roofs are very few in comparison with extensive green
roofs. This may be the result of a more widespread
construction of extensive roofs and the greater complexity
of modeling and evaluating intensive roofs. Another factor
is the low diversity of climatic types in which green
envelope performances were studied. We can discuss the
green envelopes energy efficiency according to the factors
they were classified.
7.1. Contextual factors
Firstly, we can compare the function of green roofs in
different climates. As solar radiation intensity, relative
humidity and air temperature are the main climatic factors,
which differ in different climates and affect the thermal
performance of envelopes, the comparison between green
roofs in different climatic condition can be useful.
According to the literature in tropical climates, the latent
heat dissipation plays an important role in the cooling
effect of green roofs, so airflow velocity, which helps this
phenomenon, helps cooling. It seems extensive roofs have
more efficiency than intensive ones in tropical climates
because the intensive types calm airflow on the roof
surface.
In temperate climates the latent heat dissipation is not
as important as tropical ones. It is because of the lower
relative humidity, which allows more evaporation cooling.
In winter the intensive green roof loses more thermal
energy in a tropic climate in comparison with a temperate
climate because of less soil moisture. As the intensive roof
absorbs and stores some of the reflected heat from the roof
in the air under its canopy, it is more efficient than an
extensive type for cold seasons.
Shortwave radiation is the main key factor for solar
radiation absorption in tropical climate, so shading would
be very effective to lower the surface and air temperature.
The greenery albedo is high in tropical regions because of
the more clean and clear surface of leaves as a result of
more raining and more direct solar radiation. Green roof
reduces temperature fluctuations and heat flux in cold
climates and it works as thermal insulation. Moreover, it
has the most efficiency in the summer. In temperate
climates, green roof performance is good in both warm
and cold seasons with more efficiency in warm seasons.
Green roofs increase thermal insulation, so both heat gain
and heat loss are decreased. In some regions, heat gain
reduction is up to 90%. Green roofs function efficiently in
four seasons of the humid continental climate with cold
snowy winters and hot and humid summers, with most
efficiency for cooling in the summers. In the
Dow
nloa
ded
from
ijau
p.iu
st.a
c.ir
at 2
:40
IRD
T o
n F
riday
Jun
e 1s
t 201
8
[ DO
I: 10
.220
68/ij
aup.
25.2
.100
]
108 International Journal of Architectural Engineering & Urban Planning, Vol. 25, No. 1, June 2015
Mediterranean climate, the cooling effect is good while
decrease in heat loss is not significant for winters.
Soil moisture has direct relation with roof cooling but
it has diverse effects for the roof’s thermal performance in
the winter. In monsoon climatic conditions, green roofs are
very effective for cooling. There was no considerable
research in arid climates for green envelopes in
comparison with other climatic types. In fact, most of the
studies about green roofs’ thermal performance were
conducted in temperate and tropical climates other than
harsh climates. This is despite the fact that the benefits of
greenery in harsher climates is much more necessary in
comparison with moderate climates.
For green walls in tropical climates, the thermal
insulation of the wall is increased by greenery. But in dry
continental climates, though the cooling effect was good,
the thermal performance of the green wall in winter is not
considerable. Though using indirect green walls would
decrease airflow rate behind the greenery, which would
decrease heat loss in winter by evergreen plants.
7.2. Greenery factors
In tropical climatic conditions, the greenery factors
which mainly affect the thermal performance of green
roofs are covering ratio, plants height and color. The main
biophysical processes for green roofs in the Tropics are
evapo-transpiration and albedo. While in the temperate
climate, the foliage density is the most important factor for
green roof thermal performance, in continental monsoon
climate, the leaf index area of green roof is the most
effective parameter in determining the roof’s thermal
behavior. In the tropical region, the main factors of green
walls that help cooling are coverage ratio and foliage
density. In supported green façades, the dimensions of
support structure grids affect the foliage density. Greenery
reflects much more near infrared radiation than visible
(PAR) radiation.
7.3. Impact Scale Factors
Green roofs [Table 4] and green walls [Table 5] have
considerable impacts on different scales of the built
environment. In macro scale, increasing green areas in the
urban area decreases the air temperature and CO₂ levels,
which mitigate the urban heat island effect. For building as
meso-scale, the greenery improves thermal properties of the
building envelope, which results in energy savings in
buildings. Moreover, plants help with the creation of a
microclimate with more moderate condition than the
ambient. Greenery determines the material properties of
abiotic parts of building envelope, which support it, and
affects their thermal and energetic functions in micro-scale.
7.4. Surface factors
Extensive green roofs have higher albedo than bare and
concrete roofs and its reflection is near those of white
roofs. Densely vegetated roofs in tropical climate
conditions show lower thermal insulation in comparison
with temperate climate. The green roof moisture exchange
with the environment cause it to be more energy efficient
than a bare roof.
Green wall directions influence its temperature, which
corresponds to sun path geometry and its variations
according to time. So the most cooling effect is seen in
west directions while the least is for east directions. The
south directions have higher air temperature behind the
greenery, which is small in winter. But there is a need for
more researches exploring these aspects.
Table 4 Green roofs impacts on the built environment in
different scales that are derived from literature
Green
roofs
Micro-scale
impacts Meso-scale Macro-scale
Reducing
ambient air
co2
Increasing
roof albedo
Decreasing air
temperature
Decreasing air
temperature
Increasing
roof thermal
resistance
Increasing
green areas
Table 5 Green walls impact on the built environment in different
scales, which are derived from literature
Micro-scale
impacts Meso-scale Macro-scale
Increasing
relative humidity
Increasing
passive cooling
Decreasing air
temperature
Decreasing air
temperature
Increasing wall
thermal resistance
Increasing green
areas
7.5. Integration factors
Intensive green roofs have different thermal behaviors
in comparison with extensive roofs. One reason is related
to the fact that intensive green roofs have more thickness
and mass which causes more thermal inertia than extensive
roofs and so it would store more heat. The other is related
to its larger plants and higher canopy. The intensive green
roof traps air under its canopy and so slows down the
airflow. So it decreases the heat exchange through
convection and has less efficiency in humid climates. But
in other climatic types the thermal benefits of intensive
green roof is more than the extensive ones because of
more biomass and so more biophysical functions. Green
roofs improve thermal behavior of roofs in general but the
position of the insulation layer in the roof can affect its
thermal efficiency. Inverted roof would cause a reduction
of thermal efficiency of the green roof. It is because of the
insulation is above the roofing membrane.
Living walls, especially modular panel or planted box
ones, show more cooling effect than other green wall
types. It is because of the cavity between their foliage and
the façade. Living walls create more shade so cause more
cooling effect. Also they can trap air much more than other
types inside the cavity and so reduce wind flow and create
a more distinguished microclimate inside the cavity than
other green walls, which cause more thermal insulation.
Besides, they have more mass which increases their
thermal inertia.
Dow
nloa
ded
from
ijau
p.iu
st.a
c.ir
at 2
:40
IRD
T o
n F
riday
Jun
e 1s
t 201
8
[ DO
I: 10
.220
68/ij
aup.
25.2
.100
]
E. Najafi, M. Faizi, M.A. Khanmohammadi, F. Mehdizadeh Saradj 109
Table 6. Main factors and their related variables according to discussion
Factors Type Variable Variable Variable Variable Variable
Contextual
factor
Green roof Latent heat
dissipation Calming air flow Soil moisture Shading
Thermal
resistance
Green wall Thermal resistance Calming Air flow
Impact
scale factor
Impact
Scale Micro scale Meso scale Macro scale
Green roof
Ambient air co2 Roof albedo Air
temperature
Air temperature Thermal
resistance Bio physical
Green wall
Relative humidity Passive cooling Air
temperature
Air temperature Thermal
resistance Bio physical
Surface
factor
Green roof Roof layers
materials Plant albedo
Moisture
exchange
Vegetation
dense
Green wall Geographic
directions Green density
Integration
factor
Green roof Thickness and
mass Canopy height
Bio physical
function
Position of roof
insulation
Green wall Air cavity Thickness and
mass Shading
Structure
Geometry
Greenery
factor
Green roof Plant color Plants height The leaf index
area Covering ratio
Plant
albedo
Green wall Green density Covering ratio Structure
Geometry
8. Conclusion
According to literature review we can categorize the
main factors affecting the thermal performance and energy
consumption of the buildings with green envelopes within
five main categories.
Fig. 7 Classification of factors affecting green envelops energy
efficiency
By way of a general conclusion, it can be deduced that
greenery improves the thermal performance of building
envelopes and thus results in more energy efficiency and
energy savings.
Main greenery physical properties, which affect the
green envelope thermal and energetic functions, are
density, height, LAI, covering ratio and color.
The physical, structural and geometrical properties of
surfaces, which support greenery, affect the thermal
behavior of green envelope.
Generally, green envelopes improve the thermal
function and energy performance of buildings in all
climatic conditions with most efficiency for cooling in
summers.
Arranging roof layers would influence the thermal
performance of green roofs. Properties of roof layer
materials determines the thermal behavior of green
roofs. But, improving their function depends on
climatic conditions, which determines the types of
plants and type of integration of greenery into the
envelope.
The built environment benefits from green envelopes
in different scales.
The direction and position of the green surface in
building envelope would determine its energetic role.
This study demonstrates the gaps in studying the
thermal performance of green walls in comparison with
green roofs in different climates.
Note
1. shading coefficient of plants = solar radiation beneath
plants to the solar radiation hits the plants.
2. Covering ratio= percentage of the wall area covered by
greenery.
3. Green density = surface area of leaves within covering
area.
4. Leaf shapes = categorized to simple leaf, dissected leaf,
and compound leaf.
Green envelope
Energy efficiency
Contextual factor
Surface factor
Integration factor
Greenery factor
Impact scale factor
Dow
nloa
ded
from
ijau
p.iu
st.a
c.ir
at 2
:40
IRD
T o
n F
riday
Jun
e 1s
t 201
8
[ DO
I: 10
.220
68/ij
aup.
25.2
.100
]
110 International Journal of Architectural Engineering & Urban Planning, Vol. 25, No. 1, June 2015
References
[1] Carlo Chiappi GV, Tipo, progetto, composizione
architettonica: note dalle lezioni di Gianfranco Cani,:
Alinea, 1979, p. 147.
[2] Carroll M, ed. Earthly Paradises: Ancient Gardens in
History and Archaeology. Maureen Carroll, Earthly
Paradises: Ancient Gardens in History and Archaeology,
London, British Museum Press, 2003, pp. 26-27, ISBN 0-
89236-721-0.
[3] Kaluvakolanu P. A Glimpse on the History, 2006.
[4] Clarke O. in Encyclopedia of Grapes, Harcourt Books,
2001, pp. 18-27.
[5] Rowe DB. Green roofs as a means of pollution
abatement, Environmental Pollution, 2011, Vol. 159, pp.
2100-2110.
[6] Kristin L. Gettera D. Bradley Rowea, Jeffrey A.
Andresenb. Quantifying the effect of slope on extensive
green roof stormwater retention, Ecological Engineering,
2007, Vol. 31, pp. 225-231.
[7] Castletona HF, Stovinb V, Beckc SBM, Davisonb JB.
Green roofs; building energy savings and the potential for
retrofit, Energy and Buildings, 2010, Vol. 42, pp. 1582-
1591.
[8] Lisa Kosareo RR. Comparative environmental life cycle
assessment of green roofs, Building and Environment,
2007, Vol. 42, pp. 2606-2613.
[9] C.Y. Jim SWT. Modeling the heat diffusion process in
the abiotic layers of green roofs, Energy and Buildings,
2011, Vol. 43, pp. 1341–1350.
[10] A. Spalaa HSB, Assimakopoulosb MN, Kalavrouziotisa
J, Matthopoulosa GMD. On the green roof system,
Selection, state of the art and energy potential
investigation of a system installed in an office building in
Athens, Greece, Renewable Energy, 2008, Vol. 33, pp.
173-177.
[11] Niachao A, Santamouris KPM, Tsangrassoulis A,
Mihalakaku G. Analysis of green roof thermal properties
and investigation for its energy performane Enegy and
Building, 2001, Vol. 33, pp. 719-729.
[12] Ayako Nagasea ND. Amount of water runoff from
different vegetation types on extensive green roofs:
Effects of plant species, diversity and plant structure,
Landscape and Urban Planning, 2011.
[13] Berndtsson JC. Green roof performance towards
management of runoff water quantity and quality: A
review, Ecological Engineering, 2010, Vol. 36. pp. 351-
360.
[14] CY Jim SWT. Ecological energetics of tropical intensive
green roof, Energy and Buildings, 2011, Vol. 43, pp.
2696-2704.
[15] Justyna Czemiel Berndtssona LB, Kenji Jinno. Runoff
water quality from intensive and extensive vegetated
roofs, Ecological Engineering, 2009, Vol. 35, pp. 369-
380.
[16] CY Jim SWT. Biophysical properties and thermal
performance of an intensive green roof, Building and
Environment, 2011, Vol. 46, pp. 1263-1274.
[17] Jian-feng Li a, O.W.H.W.b, Y.S. Li b, Jie-min Zhan A,
Y. Alexander Ho C, James Li d, Eddie Lam b. Effect of
green roof on ambient CO2 concentration, Building and
Environment, 2010, Vol. 45, pp. 2644-2651.
[18] Jeroen Mentens DR, Martin Hermy. Green roofs as a tool
for solving the rainwater runoff problem in the urbanized
21st century? Landscape and Urban Planning, 2006, Vol.
77, pp. 217-226.
[19] Hong-Seok Yang, J.K., Min-Sung Choi. Acoustic effects
of green roof systems on a low-profiled structure at street
level, Building and Environment, 2011.
[20] Hideki Takebayashi MM. Surface heat budget on green
roof and high reflection roof for mitigation of urban heat
island. Building and Environment, 2007, Vol. 42, pp.
2971-2979.
[21] Gabriel Pérez a, L.R.a., Anna Vila a, Josep M. González
b, Luisa F. Cabeza, Green vertical systems for buildings
as passive systems for energy savings, Applied Energy,
2011, Vol. 88, pp. 4854-4859.
[22] KJ Kontoleon EAE. The effect of the orientation and
proportion of a plant-covered wall layer on the thermal
performance of a building zone, Building and
Environment, 2010, Vol. 45, pp. 1287-1303.
[23] Gabriel Pérez1 Lr, Anna Vila1, Josep M. González2,
Luisa F. Cabeza1, Energy Efficiency of Green Roofs and
Green Facades in Mediterranean Continental Climate.
[24] Bruce G. Gregoire1, J.C.C. Effect of a modular extensive
green roof on stormwater runoff and water quality,
Ecological Engineering, 2011, Vol. 37, pp. 963-969.
[25] Chloe J. Molineuxa, Charles H. Fentimanb, Alan C.
Gangea, Characterising alternative recycled waste
materials for use as green roof growing media in the U.K,
Ecological Engineering, 2009, Vol. 35, pp. 1507-1513.
[26] Emilsson T. Vegetation development on extensive
vegetated green roofs:Influence of substrate composition,
establishment method and species mix, Ecological
Engineering, 2008, Vol. 33, pp. 265-277.
[27] Jun Yang ac, Qian Yu b, Peng Gong, Quantifying air
pollution removal by green roofs in Chicago,
Atmospheric Environment, 2008, Vol. 42, pp. 7266-
7273.
[28] Javier Almoroxa, V.H.Q., Pau Martí. Global performance
ranking of temperature-based approaches for
evapotranspiration estimation considering Köppen
climate classes, Journal of Hydrology, 2015, Vol. 528,
pp. 514-522.
[29] Deliang Chen HWC. Using the Köppen classification to
quantify climate variation and change: An example for
1901–2010, Environmental Development, 2013, Vol. 6,
pp. 69-79.
[30] T. Susca ab, S.R. Gaffin b, G.R. Dell’Osso. Positive
effects of vegetation: Urban heat island and green roofs,
Environmental Pollution, 2011, Vol. 159, pp. 2119-2126.
[31] T.C. Liu, G.S.S., W.T. Fang, S.Y. Liu, B.Y. Cheng.
Drought Tolerance and Thermal Effect Measurements for
Plants Suitable for Extensive Green Roof Planting in
Humid Subtropical Climates, Enegy and Building, 2012.
[32] Timothy Van Renterghem, D.B. Reducing the acoustical
façade load from road traffic with green roofs, Building
and Environment, 2009, Vol. 44, pp. 1081-1087.
[33] Timothy Van Renterghem D.B. In-situ measurements of
sound propagating over extensive green roofs, Building
and Environment, 2011, Vol. 46, pp. 729-738.
[34] McIntyre E.C.S.a.L. The Green Roof Manual: A
Professional Guide to Design, Installation, and
Maintenance, 2010.
[35] Cities G.R.f.H. Introduction to Green Walls: Technology,
Benefits & Design,September 2008
[36] Robert A. Francis J.L. Urban reconciliation ecology: The
potential of living roofs and walls, Journal of
Environmental Management, 2011, Vol. 92, pp. 1429-
1437.
[37] Laurenz D.R.J. Green living envelopes for food and
energy production in cities,WIT press, 2008.
Dow
nloa
ded
from
ijau
p.iu
st.a
c.ir
at 2
:40
IRD
T o
n F
riday
Jun
e 1s
t 201
8
[ DO
I: 10
.220
68/ij
aup.
25.2
.100
]
E. Najafi, M. Faizi, M.A. Khanmohammadi, F. Mehdizadeh Saradj 111
[38] Emily Voyde a, Elizabeth Fassman a, Robyn Simcock b,
Hydrology of an extensive living roof under sub-tropical
climate conditions in Auckland, New Zealand, Journal of
Hydrology, 2010, Vol. 394, pp. 384-395.
[39] G. Pérez a, L.R., A. Vila , J.M. González b, L.F. Cabeza.
Behaviour of green facades in Mediterranean Continental
climate, Energy Conversion and Management, 2011, Vol.
52, pp. 1861-1867.
[40] Dunnett N, Kingsbury N. Planting Green Roofs and
Living Walls, Portland: Timber Press, Inc, 2008.
[41] Auld H. Modeling the Urban Heat Island Benefits of
Green Roofs ion Toronto, in 1st North American Green
Roof Conference: Greening Rooftops for Sustainable
Communities, Chicago, The Cardinal Group, 2003.
[42] Alexandri, EJP. Temperature decreases in an urban
canyon due to green walls and green roofs in diverse
climates, Building and Environment, 2007.
[43] S.W. Tsang, C.Y.J. Theoretical evaluation of thermal and
energy performance of tropical green roofs, Energy,
2011, Vol. 36, pp. 3590-3598.
[44] M. Santamourisa, C.P., P. Doukasa, G. Mihalakakoub,
A.H. A. Synnefaa, P. Patargiasc. Investigating and
analysing the energy and environmental performance of
an experimental green roof system installed in a nursery
school building in Athens, Greece Energy, 2007, Vol. 32,
pp. 1781-1788.
[45] Kristin L. Gettera, D.B.R, Jeff A. Andresenb, Indrek S.
Wichmanc. Seasonal heat flux properties of an extensive
green roof in a Midwestern U.S. climate, Energy and
Buildings, 2011, Vol. 43, pp. 3548-3557.
[46] Liu K.B B. Thermal performance of green roofs through
field evaluation, in First North American Green Roof
Infrastructure Conference, Awards and Trade Show,
Proceedings for the First North American Green Roof
Infrastructure Conference: Chicago, IL, 2003.
[47] M. Zinzi SA. Cool and green roofs. An energy and
comfort comparison between passive cooling and
mitigation urban heat island techniques for residential
buildings in the Mediterranean region, Energy and
Buildings, 2011.
[48] Rakesh Kumar SCK. Performance evaluation of green
roof and shading for thermal protection of buildings,
Building and Environment, 2005, Vol. 40, pp. 1505-
1511.
[49] S. Parizotto R.L. Investigation of green roof thermal
performance in temperate climate: A case study of an
experimental building in Florianópolis city, Southern
Brazil, Energy and Buildings, 2011, Vol. 43, pp. 1712-
1722.
[50] Salah-Eddine Ouldboukhitine, R.B., Issa Jaffal, Abdelkrim
Trabelsi. Assessment of green roof thermal behavior: A
coupled heat and mass transfer model. Building and
Environment, 2011, Vol. 46, pp. 2624-2631.
[51] C.Y. Jim, S.W.T. Biophysical properties and thermal
performance of an intensive green roof, Building and
Environment, 2011, Vol. 45, pp. 1263-1274.
[52] Nyuk Hien Wonga, A.Y.K.T.a, Puay Yok Tan b, Ngian
Chung Wongc. Energy simulation of vertical greenery
systems, Energy and Buildings, 2009, Vol. 41, pp. 1401-
1408.
[53] Katia Perini a, Marc Ottelé b, A.L.A. Fraaij b, E.M. Haas
b, Rossana Raiteri. Vertical greening systems and the
effect on air flow and temperature on the building
envelope, Building and Environment, 2011, Vol. 46, pp.
2287-2294.
[54] Chi Feng, Q.M., Yufeng Zhang. Theoretical and
experimental analysis of the energy balance of extensive
green roofs, Energy and Buildings, 2010, Vol. 42, pp.
959-965.
[55] Yi-Jiung Lin a, b, Hsien-Te Lin c,d. Thermal
performance of different planting substrates and
irrigation frequencies in extensive tropical rooftop
greeneries, Building and Environment, 2011, Vol. 46, pp.
345-355.
[56] G Papadakis, P Tsamis, S Kyritsis. An experimental
investigation of the effect of shading with plants for solar
control of buildings, Energy and Buildings, 2001, No. 8,
Vol. 33, pp. 831=836.
[57] G. Péreza, L.R., A. Vilaa, J.M. Gonzálezb, L.F. Cabezaa.
Behaviour of green facades in Mediterranean continental
climate, Energy Conversion and Management, 2011, No.
4, Vol. 52, pp. 1861-1867.
[58] Mr. Liao Zaiyi, D.N.J.L. Study On Thermal Function Of
Ivy-Covered Walls.
[59] Miller A, S.K., Lam M. Vegetation on building facades,
Bioshader, 2007.
[60] M, K., Rain water management with green roofs and
living walls, 2007.
[61] Köhler, M. Green facades a view back and some visions.
Urban Ecosystem, 2008, Vol. 11, pp. 423-436.
[62] Hoyano. Climatological uses of plants for solar control
on the effects on thethermal environment of a building.
Energy and Buildings, 1988, Vol. 11, pp. 181-9.
[63] Julià Coma, G.P., Cristian Solé, Albert Castell, Luisa F.
Cabeza. New Green Facades as Passive Systems for
Energy Savings on Buildings. Energy Procedia, 2014,
Vol. 57, pp. 1851-1859.
[64] Diana E. Bowler, L.B.-A., Teri M. Knight, Andrew S.
Pullin, Urban greening to cool towns and cities: A
systematic review of the empirical evidence. Landscape
and Urban Planning, 2010, Vol. 97, pp. 147-155.
[65] Newton J, G.D., Early P, Wilson S. Building greener
guidance on the use of green roofs, green walls and
complementary features on buildings, London, UK,
CIRIA, 2007.
[66] Scherba. Modeling impacts of roof reflectivity, integrated
photovoltaic panels and green roof systems on sensible
heat flux into the urban environment, Building and
Environment, 2011, Vol. 46.
[67] Wong N.H. The effects of rooftop gardens on energy
consumption of a commercial building in singapore.
Energy and Buildings, 2003, Vol. 35.
[68] Adam Scherba, D.J.S, Todd N. Rosenstiel, Carl C.
Wamser. Modeling impacts of roof reflectivity,
integrated photovoltaic panels and green roof systems
on sensible heat flux into the urban environment.
Building and Environment, 2011, Vol. 46, pp. 2542-
2551.
[69] Van Bohemen HD, F.A., Ottele M. Ecological
engineering, green roofs and the greening of vertical
walls of buildings in urban areas, in Ecocity World
Summit,. 23 April 2008: San Francisco, California,
USA.
[70] Nyuk Hien Wong a, A.Y.K.T.a., Yu Chen a, Kannagi
Sekar a,b, Puay Yok Tan b, K.C.b. Derek Chan b, Ngian
Chung Wong c. Thermal evaluation of vertical greenery
systems for building walls. Building and Environment
2010, Vol. 45, pp. 663-672.
Dow
nloa
ded
from
ijau
p.iu
st.a
c.ir
at 2
:40
IRD
T o
n F
riday
Jun
e 1s
t 201
8
[ DO
I: 10
.220
68/ij
aup.
25.2
.100
]